1. Field of the Invention
The present invention relates to an image providing method and device which nonlinearly develops on a display plane an image in any sight-line direction in a fish-eye image (omnidirectional image), and more particularly, to an interactive type image providing method and device which can provide in real-time an moving image in a direction intended by an observer.
2. Description of the Related Art
In a monitoring system using a monitoring camera, for example, a method is known for collecting a wide-angle image using a monitoring camera with a fish-eye lens instead of a monitoring camera with a usual lens to obtain a wider monitorable area. In this case, a monitoring camera with a fish-eye lens provides an fish-eye image more distorted than an image provided by a monitoring camera with a usual lens. A non-linear transformation processing is thus known that displays on a plane a distortion-removed image in any sight-line direction from the fish-eye image. Such a non-linear transformation processing is referred to a normalization processing (dewarp).
Known methods for dewarping a fish-eye image include, for example, methods disclosed in Japanese patents No. 3051173 and No. 3126955. Dewarping logics are formulated into transformation equations that are generally similar. The dewarping methods have thus been implemented as a device with a programming language using any transformation equation, or implemented after fixing areas to be drawn at a plurality of places and creating previously a transformation rule in a table-lookup form based on a equation.
In the method disclosed in Japanese patent No. 3051173 on page 5 in the right column for lines 19 through 30 and FIG. 4, X-MAP processor and Y-MAP processor speed up the mapping on a sphere. Also in the method disclosed in Japanese patent No. 3126955 on page 5, paragraph 0021, and FIG. 1, two coordinate-operation parts use a look-up table to speed up the coordinate computation on a sphere.
In both methods disclosed in above-mentioned Japanese patents No. 3051173 and No. 3126955, however, a non-linear transformation processing uses a mapping on a sphere as a basis to sequentially calculate display pixels, and the dewarping is only performed in visual fields from a plurality of predetermined limited places, thereby providing poor interactivity.